1. Technical Field
The present invention relates to a method and an apparatus for detecting the shape of an object.
In many applications it is important to precisely know the outer shape of an object. One such application is, for example, in the field of medical technology. Patients are scanned, e.g., by means of computer tomography (CT), to determine the location of a tissue change in the body or in a body part prior to undergoing surgery or radiotherapy. During this, markers or emphasized points on the body part are included in the scan, the positional data of which is used later in a surgical navigation system, which monitors the treatment room during the operation in order to assist the surgeon or radiotherapist.
2. Description of Related Art
Disadvantageously, in such methods, a complicated assignment of the positional data from the CT scan to the three-dimensional data in the operating room with the aid of the navigation system must occur prior to treatment. On the one hand, this assignment is time-consuming since corresponding markers need to be applied manually to the skin, accessed by a referencing device, and identified. On the other hand, the assignment is quite often inaccurate, since, for example, skin markers may move slightly out of place in the course of the referencing procedure. Automatic referencing procedures using markers or by means of natural landmarks are highly computing-intensive.
Another disadvantage of such methods for assigning location and shape is that they do not necessarily reproduce the precise actual location data for the outer shape or inner shape at the time of treatment or operation, the shape data stemming namely from a CT scan implemented, for example, some time before the operation and only the mapped positions of the markers are updated. The position of tissue points relative to the markers may change due to shifting from the time taken to furnish the CT scan data to the operating room, with the result that the detected shape and location in the navigation system is incorrect and may lead to inaccurate treatment.